Position responsive potential divider



July 3, 1962 D. M. PARK 3,

POSITION RESPONSIVE POTENTIAL DIVIDER Filed Aug. 21, 1961 2 Sheets-Sheet 1 [LI 0 2 U) LIJ O:

. l Z 2 II LIJ DEGREES TILT FIG. 4

DONALD M. PARK INVENTOR.

ATTORNEY .IIII

July 3, 1962 D. M. PARK 3,042,888

POSITION RESPONSIVE POTENTIAL DIVIDER Filed Aug. 21, 1961 2 Sheets-Sheet 2 DONALD M. PARK INVENTOR.

ATTORNEY s4 Sk United States Patent 3,042,888 P0ITION RESPONSWE POTENTIAL DIVIDER Donald M. Park, Raleigh, N.C., assignor to Park-Baker Electronic Development Corporation, Raleigh, N.C., a corporation of North Carolina Filed Aug. 21, 1961, Ser. No. 132,964 12 Claims. (Cl. 33844) My invention is concerned with an electrical device which acts as a potential divider and which employs an electrically conductive liquid element, the position of which with respect to the other elements in the device determines the manner in which the potential is divided.

An object of this invention is to provide an electrical potential dividing device which when it has applied to it a given input voltage, produces an output voltage that is dependent on both the amount of such applied voltage and the physical position of the device at the time.

Another object is to provide an electrical potential dividing device having an output voltage that can be regulated by change of position of the device.

-Another object is to provide an electrical potential dividing device of the kind previously mentioned and which is substantially noiseless in its operation.

Another more specific object of the invention is to provide a position sensitive electrical potential dividing device of this kind which is adapted to being mounted on pedals in pedal controlled electronicmusical devices such as electronic organs.

A further object is to provide an electrical potential dividing device of the kind mentioned which is capable of producing a gradually changing control voltage such as for audio circuitry.

These and other objects of the invention will become apparent from the description and in the drawings, in which:

the invention.

FIGURE 2 is a plan view of the FIGURE 1 device.

FIGURE 3 shows the FIGURE 1 device in a tilted position,

FIGURE 4 is a curve showing variation of terminal resistances of the FIGURE 1 device.

FIGURE 5 illustrates a typical circuit application of the invention.

FIGURE 6 illustrates how the pedal controlled device.

FIGURE 7 is a side view of another embodiment of the invention.

FIGURE 8 is a plan view of the FIGURE 7 device.

FIGURE 9 shows the FIGURE 7 device in a tilted position.

FIGURE 10 is a side View of a third embodiment of the invention.

FIGURE 11 is a plan view of the FIGURE 10 device.

FIGURE 12 shows the FIGURE 10 device in a tilted position.

FIGURE 13 is a schematic cross section of a further embodiment of the invention.

FIGURE 14 is a perspective view of an alternative form of the inventions conducting element.

FIGURE 15 is a schematic cross section of an additional embodiment utilizing the element of FIGURE 14.

invention is applied to a remains substantially the same.

3,042,888 Patented July 3, 1962 ice In general, the invention comprises a hollow, sealed housing containing within and at the bottom of the housing, a pool of relatively low resistance, electrically conducting liquid such as ethylene glycol. The chamber or cavity within the housing in which the liquid is confined may vary in shape as later described but in all instances the liquid fills less than the full volume of the chamber in order that the liquid may shift position as the housing is tilted. Three conductors extend from respective external terminals through the housing and terminate at isolated points in the chamber. The three conductors are electrically insulated one from the other externally of the chamber.

A series electrical path including two of the mentioned conductors is established through the housing and between external terminals such that this path may be included in other circuitry. The series path includes a strip of material of normally high resistance but which has an aflinity for the conducting liquid such that when the liquid and material come in contact, the material experiences a substantial drop in resistance. For example, a relatively stifi', absorbent paper meets these characteristics. The mentioned material is fixed in position within the housing and is normally at least partially in contact with the liquid. The extent to which the material is in contact with the liquid, however, varies with the tilt of the housing and, accordingly, the resistance of different portions of the material changes as they become more or less wet with the liquid according to the tilt of the housing. In general, however, the material is so fixedly located and shaped with respect to the liquid that, as the housing tilts within its normal range of operation, the overall series path resistance preferably remains substantially constant. That is, as certain portions become relatively Wet, other portions become relatively dry and the net series resistance Other modes of behaviour may be obtained by varying the shape of the material and its position with respect to the liquid.

Between the ends of the described series path and normally always in electrical contact with the conducting liquid, the third of the mentioned conductors, a relatively low resistance metallic conductor, is employed. Thi last conductor has a resistance that remains independent of liquid position and it acts to shunt current from the series path and direct it to a third external terminal. Like the series path, this shunt path may also be tied into external circuitry for control purposes. The shunt terminal is electrically insulated from each of the series terminals except through a shunt path that includes the low resistance conductor, some of the liquid conductor and portions of the material.

As the described housing is tilted, the amount of resistance between the shunt terminal and each respective series terminal varies and in a diiierent manner with respect to each series terminal, since between each series terminal and the shunt terminal there appears a given amount of the previously mentioned material whose resistance varies with housing position because of varying contact with the liquid. By impressing a given voltage across the series terminals, a control voltage can be taken off between the shunt terminal and one of the series terminals and this voltage will vary with position of the housing. The device thus acts as a position sensitive potential divider and it is in control applications that the invention appears to exhibit its greatest advantages.

The invention may take many forms. In FIGURES l, 2 and 3 there is illustrated an embodiment which has been found to be relatively simple to manufacture and dependable in operation. In these figures, 2% represents a hollow, sealed, rectangular housing comprised of relatively thin, transparent, electrically non-conducting plastic walls. Housing includes end walls 21, 22, side walls 23, 24, bottom wall and top wall 26. Leading to housing 20 are three electrical leads having conductors 27, 28 and 29 respectively as shown in the drawings. Conductor 29 passes through end wall 21 and within housing 20 is stripped of its conventional insulating covering 36 so as to present a bare metallic conductor, as at 31. Conductor 27 also passes through end wall 21 and within housing 20 is suitably stripped and connected physically and electrically to one end of a relatively stiff, absorbent paper arch 32. Conductor 28 at the opposite end of housing 20 passes through end wall 22 and in a similar manner is physically and electrically connected to the opposite end of the paper arch 32. All of the various openings through which the conductors 27, 28 and 29 pass into the housing are sealed by suitable cement to maintain the housing 20 in a liquid tight condition.

Partially filling the interior of housing 2d is an electrically conducting liquid indicated in dash lines at 33. In addition to being electrically conducting, this liquid should also be chosen so as to be relatively inert with respect to the other components of the device with which the liquid comes in contact within the housing. It will be noted in FT URE 1 that the level of this liquid partially saturates each end of the arch 32 whereas in the tilted position of FIGURE 3 more of one end of arch 32 is submerged in liquid 33 than is the other. T1 and T2 may be considered as the ends of a series electrical path which includes conductors 27, 23 and arch 32. Terminal T4 may be considered to be the terminal of a shunt path that includes conductor 31, this being an extension of conductor 29, and liquid 33 up to the point that it contacts arch 32. When the housing is in the level position of FIGURE 1, it can be seen that the resistance between the terminals T-l and T3 is substantially equal to the resistance between terminals T-2 and T3. Gn the other hand, when the housing is tilted to the position in FEGURE 3, the resistance between T4 and T-3 now becomes substantially higher than is the resistance between T-Z and T3 since the arch 32 at its end near terminal T2 is substantially fully saturated by liquid 33 whereas the opposite end of arch 32 proximate terminal T-1 is substantially dry. At the same time, due to the shape of arch 32, the resistance between T1 and T2 remains substantially the same.

The electrical behaviour of the device is generally illustrated in FIGURE 4 where we assume that one direction of tilt is considered positive and the other direction of tilt is considered negative. From this it can be seen that the shunt resistance between the shunt terminal and one series terminal such as T1 to T3 varies oppositely to the resistance between the shunt terminal and the other series terminal such as T3 to T2. That is, if we consider tilting to the right as in FIGURE 3 to be a positive tilting, then the resistance between T-2 and T3 would gradually become less as the housing 20 is tilted to the right. Likewise, tilting to the left would cause the resistance between T-2 and T1 to gradually become less. It has been found that this change is, in fact, gradual even though the housing is moved rela tively rapidly, due to the time required for the liquid 33 to come in electrical contact with the arch 32. In FIGURE 4, note is also made of the generally steady state condition of resistance T-l to T-Z. The precise shape and values of curves such as those illustrated in FIGURE 4 will of course vary according to the shape 4 of arch 32, the particular conducting liqui and other design factors that are chosen which might aflect the terminal resistances. The curves of FIGURE 4 are, therefore, only representative of the general behaviour of the invention. By changing some of the factors mentioned, these curves can in fact be made to assume other shapes such as might be desired for special applications.

Simply as one example of where the invention may be applied, there is shown in FIGURE 5 a portion of a resistance coupled audio amplifier circuit in which the terminals TI., T4. and T3 are represented, in accordance with the positions they might occupy in such circuitry. From this circuit diagram, it can be seen that with a given voltage across T1 to T2, the voltage applied by shunt terminal T-S to grid 35 can be varied according to the position of housing 2%, schematically indicated by dotted lines in FIGURE 5 as 2t). If housing 20 is attached to a foot pedal such as pedal 36 some- What schematically represented in FIGURE 6 as being adapted to rock around an axis 37 and the terminals T-l, T2 and T3 are arranged in a circuit such as shown in FIGURE 5, the circuit can be controlled by pedal operation. Such an application is particularly important in electronic organs, where it is desired to control the volume of electrical music sources through such pedal operation. It should of course be understood that the particular mode of control can be varied by changing such things as the shape and location of arch 32, the type of liquid 33 and the size and shape of housing 20.

In FIGURES 7, 8 and 9, there is shown another embodiment of the invention. In these figures, 40 reprc seats a plastic block which has properties of being transparent and non-conductive. Block 4%) is so manufactured as to include a somewhat elliptical shape closed tubular channel within its interior and which is indicated genorally at 41. This may be accomplished, for example, by molding two block halves each including the channel and then welding the two half blocks together. Conductors 42, 43 and 44 pass through block 4-0 at the respective points indicated in the drawings. Within the lower portion of the elliptical channel 41 there i placed a relatively stiff, absorbent paper strip 46. Conductor 42 is physically and electrically connected to one end of paper strip 46, whereas conductor 43 is physically and electrically connected to the opposite end of paper strip 46. Conductor 44 is arranged to be physically and electrically connected to an intermediate point on paper strip 46 as indicated in these figures. An electrically conducting liquid indicated by the heavy shading at 47 partially fills a portion of the elliptical channel 41 that is occupied by strip 46.

Using the same designation of terminals, T1, T2 and T-3, it can be seen that this embodiment of the invention illustrated by FIGURES 7, 8 and 9 also furnishes what is in effect a potential divider in that, as block 40 is tilted as in FIGURE 9, the resistance between T-l and T3 will vary oppositely from the resistance between T-2 and T--3 such that, if a voltage is applied to the terminals T-l and T-2 there can be obtained an output voltage at T-l to T-3 which will vary with the position of housing block 46.

In FIGURES 10, 11 and 12, there is illustrated a third embodiment of the invention in which the liquid forms a part of the series path. In these figures, 50 represents a housing of construction similar to housing 20 of FIG- URE 1. Passing through end wall 51 there is a conductor 52 and through end wall 53 a conductor 54. Also passing through end wall 51 is a conductor 55 having an exposed surface as at 56. Supported at its upper end and electrically connected to conductor 52 is an absorbent conducting member 57 that curves downwardly and is fixed at its lower end to the inner surface of end wall 53. A similar curved absorbent conducting member 58 is supported at its upper end by conductor 57 and at its lower end is fixed to the inner surface of end wall 51. Within housing 56, a suitable electrically conducting liquid 59 serves to bridge the space between members 57, 53. As the housing tilts, as in FIGURE 12, the portions of members 57, 53 that are in contact with liquid. 59 will change and accordingly the previously mentioned resistance variation between respective terminals T-l, T-2 and T-3 is obtained.

I have shown in FIGURE 13 somewhat schematically a fourth embodiment of the invention in which 70 represents in cross section a curved electrically conducting metal tube. Within this metallic tubular housing there is mounted a thin curved paper member 71 which is physically and electrically connected to and supported from two conductors 72 and 73. Conductors 72, '73 are electrically insulated by suitable means 74, 75 from tube 78 and within tube 70 there is placed a suitable amount of electrically conducting liquid as indicated by the dashed line '76. Member 71 contacts the liquid but is supported free of the tube 76. A third conductor makes electrical contact with the metal tube 70 as indicated at 78. In this example, it can be seen that whenever tube '76 is tilted, whether to the right or to the left, as around axial point A, the resistance between terminals T-l and T4: and between T-2 and T-3 respectively will vary according to the position of the tube 76. Thus, if a given voltage is applied across terminals T-l to T -2, an output voltage can be obtained either between terminals T-l to T-3 or between terminals T-2 to T3 which will vary according to the position of housing 7ii.

In FIGURES l4'and 15, there is schematically illustrated a fifth embodiment in which the bridge between the series terminals is considered to be in the form of a slot-ted band 80 adapted to rotate around a horizontal axis X while residing in an electrically conducting liquid 81 indicated by dashed lines, the liquid being confined in a tubular electrically non-conducting housing 82.. Band 80 is supported by and is electrically connected to conductors 83, 84 passing through the Wall of housing 82 through which also passes a third conductor 85 which makes contact with liquid 81. As the structure of this embodiment tilts about axis X, it will be seen that the resistance variation previously described between tenninals T-1, T2 and T-3 will be obtained.

Many other variations of the invention will become apparent to those skilled in the art. The series bridge elements may, for example, assume special shapes for special applications such as to induce different modes of electrical behaviour in diiferent directions of tilt. Various electrically conducting liquids and various absorbent or adsorbent conducting materials such as carbon, various forms of paper, conducting and absorbent rubbers and the like may be used as the series bridge elements, all such modifications being within the scope of the invention as defined by the appended claims. The word absorbent in the claims is intended to cover both absorbent and adsorbent type bridge element wherein the effective electrical resistance of the element is substantially lowered where the element contacts the conducting liquid.

Having thus explained my invention, what I claim is:

1. A position responsive potential dividing device comprising a sealed housing including a chamber therein and being adapted to tilt from a normal position in varying amounts and directions; and electrically conducting liquid partially filling said chamber and adapted to shift position with said tilt; first, second and third electrical conductors extending from respective external terminals through said housing into and terminating at isolated points within said chamber, said conductors being electrically insulated externally of and having exposed electrically conducting surfaces within said chamber; conducting means absorbent to said liquid fixedly positioned Within said chamber and electrically. connected to certain of said surfaces whereby to form part of a series electrical path which includes two of said points and the respective terminals associated therewith and a shunt electrical path which includes said other point and its terminal, said series path including said absorbent conducting means and said shunt path including said liquid in all positions normally assumed by said housing; said tilt acting to vary the contact between said absorbent conducting means and said liquid whereby to vary the electrical resistance between pairs of said points in a predetermined manner thereby enabling a voltage applied across the terminals connected to said two points to divide through said other point and the terminal connected theretoaccording to the amount and direction of said tilt.

2. A device as claimed in claim 1 in which said absorbent conducting means when dry exhibits a resistance that is relatively high with respect to the resistance of said liquid.

3. A device as claimed in claim 1 whereby said first and second conductors are longitudinally spaced within said chamber and said absorbent conducting means assumes the form of a shaped strip of material extending between, electrically connected to, and supported from said first and second conductors and resides in said normal position above said third conductor.

4. A device as claimed in claim 3 wherein said absorbent conducting means is of such material and is so positioned and shaped as to maintain a substantially constant electrical resistance between said two points in positions normally assumed by said housing during said tilt.

5. A device as claimed in claim 1 in which said absorbent conducting means comprises relatively stiff paper absorbent to said liquid.

6. A device as claimed in claim 1 in which said absorbent conducting means comprises a single integral member directly electrically connected to said first and second conductors and electrically insulated from said third conductor except through said liquid.

7. A device as claimed in claim 1 in which said absorbent conducting means comprises a single integral member electrically connected to each of said conductors at said points.

8. A device as claimed in claim 1 in which said absorbent conducting means comprises a pair of spaced members each having one end directly connected to one of said surfaces and another end in contact with said liquid.

9. A device as claimed in claim 1 in which said housing is formed of an electrically insulating material thereby acting to insulate electrically said conductors externally of said chamber.

-10. A device as claimed in claim 1 wherein said housing is of an electrically conducting material in electrical contact with said liquid, one of said conductors is directly electrically connected to said housing, the other two of said conductors are electrically insulated from said housing and said absorbent conducting means is so supported within said housing as to be free of physical contact therewith.

11. A device as claimed in claim 1 wherein said chamber is tubular in form.

12. A foot operated position responsive potential dividing device comprising a pivotedly mounted pedal, a sealed housing mounted on said pedal and including a chamber therein and being adapted to tilt with motion of said pedal from a normal position in varying amounts and directions; an electrically conducting liquid partially filling said chamber and adapted to shift position with said tilt; first, second and third electrical conductors extending from respective external terminals connected to circuitry controlled by said device to and through said housing into and terminating at isolated points within said chamber, said conductors being electrically insulated externally of and having electrically conducting surfaces within said chamber; conducting means absorbent to said liquid fixedly positioned Within said chamber and electrically connected to certain of said surfaces whereby to form part of a series electrical ath which includes two of said points and the respective terminals associated therewith and a shunt electrical path which includes said other point and its terminal, said series path including said absorbent conducting means and said shunt path including said liquid in all positions normally assumed by said housing; said tilt acting to vary the contact between said absorbent conducting means and said liquid whereby to vary the electrical resistance between pairs of said points in a predetermined manner thereby enabling a voltage applied within said circuitry and across the terminals connected to said two points to divide through said other point and the terminal connected thereto according to the amount and direction of said tilt as effected by motion of said pedal.

References Cited in the file of this patent UNlTED STATES EATENTS 857,138 Wobber June 18, 1907 1,614,774 Bonine Jan. 18, 1927 2,534,439 Alkire Dec. 19, 1950 2,671,153 Ray et al. Mar. 2, 1954 2,977,559 Rosenberg Mar. 28, 1961 

